Solar cell

Abstract

An embodiment of the present invention provides a solar cell comprising a plurality of holes penetrating the solar cell, wherein the plurality of holes satisfy at least one of conditions 1 to 3. <Condition 1> The plurality of holes have two or more shapes. <Condition 2> A distance (D1) between a first hole, which is one of the plurality of holes, and a hole adjacent to the first hole in an X-direction, and a distance (D2) between a second hole, which is one of the plurality of holes, and a hole adjacent to the second hole in the X-direction differ from each other. <Condition 3> A distance (D3) between a third hole, which is one of the plurality of holes, and a hole adjacent to the third hole in a Y-direction, and a distance (D4) between a fourth hole, which is one of the plurality of holes, and a hole adjacent to the fourth hole in the Y-direction differ from each other.

Description

solar cells

[0001] The present invention relates to a solar cell. More specifically, the present invention relates to a transparent solar cell with improved viewing angle and pattern visibility.

[0002] This invention was made possible with funding from the Ministry of Trade, Industry and Energy under project number 2410002578 titled "Development of low-power driveable color-changing BIPV technology".

[0003] This invention was made possible with funding from the Ministry of Science and ICT under project number 2710017811 titled "Development and Demonstration of an Integrated Energy Saving-Production-Utilization Package for the Conversion of Existing Buildings to ZEB".

[0004] Recently, as the depletion of conventional energy resources such as oil and coal is anticipated, interest in alternative energy sources to replace them is growing. Among these, solar cells are gaining attention as next-generation batteries that directly convert solar energy into electrical energy using semiconductor devices.

[0005] Meanwhile, transparent solar cells are next-generation solar cells capable of significantly expanding their application fields by overcoming the various limitations of conventional opaque solar cells, and development is underway based on various materials such as dye-sensitized materials and perovskites. Among these, selective light-transmitting structure formation technology utilizing invisible micro-hole structures enables the realization of transparent solar cells regardless of the material. Furthermore, active research is being conducted in this area due to the advantages of freely adjustable transmittance and colorless characteristics.

[0006] However, existing selective light-transmitting structure formation technology has a problem in that when the pattern size is increased to widen the viewing angle, image distortion and interference patterns (e.g., moiré patterns) located behind the transparent solar cell occur as the pattern begins to be recognized.

[0007] Therefore, there is a demand for transparent solar cells that improve the viewing angle while reducing pattern recognition.

[0008] Embodiments of the present invention provide a transparent solar cell with an excellent viewing angle and reduced pattern recognition.

[0009] One embodiment of the present invention provides a solar cell comprising a plurality of holes penetrating the solar cell, wherein the plurality of holes satisfy at least one of the following conditions 1 to 3.

[0010] <Condition 1>

[0011] The above plurality of holes includes two or more types.

[0012] <Condition 2>

[0013] The distance (D1) between the first hole, which is one of the plurality of holes, and the hole adjacent to the first hole in the X direction, and the distance (D2) between the second hole, which is one of the plurality of holes, and the hole adjacent to the second hole in the X direction are different from each other.

[0014] <Condition 3>

[0015] The third hole, which is one of the plurality of holes, and the distance (D3) between the third hole and the hole adjacent in the Y direction, and the fourth hole, which is one of the plurality of holes, and the distance (D4) between the fourth hole and the hole adjacent in the Y direction are different from each other.

[0016] In this embodiment, the plurality of holes can satisfy condition 1.

[0017] In this embodiment, the shape of the hole may be at least one of an elliptical shape, a cross shape, a polygonal shape, a star shape, or a shape in which two or more ellipses are superimposed.

[0018] In this embodiment, the plurality of holes may satisfy at least one of condition 2 and condition 3.

[0019] In this embodiment, among the plurality of holes, the number of combinations of the first hole and the second hole satisfying condition 2 may be 2 or more.

[0020] In this embodiment, the number of combinations of the third hole and the fourth hole satisfying condition 3 among the plurality of holes may be 2 or more.

[0021] In this embodiment, the size of each of the plurality of holes may be 1 μm to 5 mm.

[0022] In this embodiment, the area occupied by the plurality of holes in the solar cell may be greater than 0% and less than or equal to 90% of the total area of ​​the solar cell.

[0023] In the present embodiment, the solar cell comprises a crystalline silicon substrate; a first layer located on the upper or lower surface of the crystalline silicon substrate and forming a PN junction with the crystalline silicon substrate; a first electrode portion electrically connected to the first layer; a second layer located on the lower surface of the crystalline silicon substrate; a second electrode portion electrically connected to the second layer; and an optical film disposed on the upper surface of the crystalline silicon substrate, wherein the plurality of holes can each penetrate the optical film and the crystalline silicon substrate.

[0024] In the present embodiment, the solar cell may further include at least one of a protective film, an anti-reflective film, and an optical film disposed on the upper surface of the crystalline silicon substrate.

[0025] In the present embodiment, the protective film or the anti-reflective film is further included, and the anti-reflective film or the protective film may be disposed from the upper surface of the crystalline silicon substrate to at least a portion of the inner surfaces of the plurality of holes.

[0026] In the present embodiment, the crystalline silicon substrate has a first conductivity type, the first layer is an emitter layer doped with impurities having a second conductivity type opposite to the first conductivity type, and the second layer may be a back-side electric field layer doped with impurities having the first conductivity type.

[0027] In the present embodiment, one of the first layer and the second layer may be an electron transport layer comprising an electron transport material, and the other of the first layer and the second layer may be a hole transport layer comprising a hole transport material.

[0028] In the present embodiment, the first layer and the second layer are alternately arranged on the lower surface of the crystalline silicon substrate, and the plurality of holes can each penetrate the first layer and the first electrode portion or the second layer and the second electrode portion.

[0029] In the present embodiment, the first layer is disposed on the upper surface of the crystalline silicon substrate, the second layer is disposed on the lower surface of the crystalline silicon substrate, and the plurality of holes can penetrate the first layer and the first electrode portion and the second layer and the second electrode portion.

[0030] The solar cell according to the embodiments includes a plurality of holes that penetrate the solar cell and satisfy at least one of conditions 1 to 3, thereby improving the viewing angle of the solar cell and reducing pattern recognition. Accordingly, while having a wide viewing angle, it is possible to effectively prevent problems such as the image appearing distorted or interference patterns like moiré patterns being recognized due to pattern recognition. Of course, the scope of the present invention is not limited by these effects.

[0031] FIGS. 1 to 3 are schematic plan views illustrating the upper surface of a solar cell according to one embodiment of the present invention.

[0032] FIG. 4 is a schematic plan view illustrating the upper surface of a solar cell according to Comparative Example 1.

[0033] FIGS. 5 to 7 are cross-sectional views schematically illustrating a cross-section of a solar cell according to one embodiment of the present invention.

[0034] Figure 8 is an image showing the result of observing writing using a solar cell according to Example 1.

[0035] Figure 9 is an image showing the result of observing writing using a solar cell according to Comparative Example 1.

[0036] Figure 10 is an image showing the result of observing writing using a solar cell according to Comparative Example 2.

[0037] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention.

[0038] Terms such as "first," "second," etc., may be used to describe various components, but components should not be limited by these terms. Terms are used solely for the purpose of distinguishing one component from another.

[0039] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. Additionally, in each figure, components are exaggerated, omitted, or schematically depicted for convenience and clarity of explanation, and the size of each component does not entirely reflect its actual size.

[0040] In the description of each component, where it is stated that it is formed on or under, "on" and "under" include both forms formed directly or through other components, and the criteria for "on" and "under" are explained based on the drawings.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing with reference to the accompanying drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0042] FIGS. 1 to 3 are schematic plan views illustrating the top surface of a solar cell according to one embodiment of the present invention. FIG. 4 is a schematic plan view illustrating the top surface of a solar cell according to a comparative example.

[0043] Referring to FIGS. 1 to 3, in a solar cell (100) according to one embodiment, the solar cell (100) includes a plurality of holes (H) penetrating the solar cell (100), wherein the plurality of holes (H) may satisfy at least one of the following conditions 1 to 3.

[0044] <Condition 1>

[0045] The above plurality of holes includes two or more types.

[0046] <Condition 2>

[0047] The first hole (H1), which is one of the plurality of holes, and the distance (D1) between the first hole (H1) and the adjacent hole in the X direction, and the second hole (H2), which is one of the plurality of holes, and the distance (D2) between the second hole (H2) and the adjacent hole in the X direction are different from each other.

[0048] <Condition 3>

[0049] The third hole (H3), which is one of the plurality of holes, and the distance (D3) between the third hole (H3) and the hole adjacent in the Y direction, and the fourth hole (H4), which is one of the plurality of holes, and the distance (D4) between the fourth hole (H4) and the hole adjacent in the Y direction are different from each other.

[0050] For example, if the plurality of holes satisfies one of conditions 1 to 3, not only is the viewing angle improved, but pattern recognition can also be effectively reduced.

[0051] For example, in a solar cell containing a plurality of holes penetrating the solar cell, if any one of conditions 1 to 3 is not satisfied and a plurality of holes having the same shape are regularly arranged, the viewing angle may be narrow, or if the size of the holes is increased to widen the viewing angle, the hole pattern may be recognized, and the image viewed through the transparent solar cell may appear distorted due to an optical illusion, or interference patterns (e.g., moiré patterns, etc.) may be visible.

[0052] However, when the above-mentioned plurality of holes (H) satisfy conditions 1 to 3, the viewing angle is widened, and even if the size of the holes (H) is made large to widen the viewing angle, the problem of appearing distorted due to optical illusion or interference patterns due to the diverse shapes of the holes (H) or the irregular arrangement of the holes (H) can be improved.

[0053] To verify this, the viewing angle was measured for a solar cell (Comparative Example 1) in which holes (H) penetrating the solar cell are arranged as shown in FIG. 4, the size of the holes (H) is 260 μm, and the spacing between the holes (H) is 250 μm; a solar cell (Comparative Example 2) in which holes (H) penetrating the solar cell are arranged as shown in FIG. 4, the size of the holes (H) is 100 μm, and the spacing between the holes (H) is 100 μm; and a solar cell (Example 1) in which holes (H) penetrating the solar cell are arranged as shown in FIG. 1, and the size of the holes (H) is 260 μm, and the results are shown in Table 1 below.

[0054] In addition, the results of observing the writing using the solar cell according to Example 1, the solar cell according to Comparative Example 1, and the solar cell according to Comparative Example 2 are shown in FIGS. 7, FIGS. 8, and FIGS. 9, respectively.

[0055] Example 1 Comparative Example 1 Comparative Example 2 Transmittance 20% 20% 20% Viewing Angle 120° (degrees) 120° (degrees) 56° (degrees)

[0056] Referring to Table 1 and Figures 7 to 9, in Example 1, large holes (H) are irregularly arranged, so the viewing angle is wide and the text is observed more clearly as shown in Figure 7. On the other hand, in Comparative Example 1, the holes (H) are large and the viewing angle is wide, but the holes (H) are regularly arranged and the text is observed distorted as shown in Figure 8. In Comparative Example 2, the holes (H) are small and the text is observed clearly as shown in Figure 9, but it can be confirmed that the viewing angle is narrow.

[0057] Referring to FIGS. 1 and 2, the plurality of holes (H) can satisfy condition 1. In this case, when observing the upper surface of the solar cell (100), the shape of the recognized holes (H) may be two or more types. For example, the shape of the holes (H) includes cases where the angle is different for holes (H) of the same shape.

[0058] According to one embodiment, the plurality of holes (H) may include three or more shapes, four or more shapes, five or more shapes, or ten or more shapes.

[0059] According to one embodiment, the plurality of holes (H) may each have shapes that are all different from each other.

[0060] According to one embodiment, the plurality of holes (H) may include at least one of an elliptical shape, a cross shape, an X shape, a polygonal shape, a star shape, or a shape in which two or more ellipses are superimposed.

[0061] According to one embodiment, with reference to FIGS. 2 and FIGS. 3, the plurality of holes (H) may satisfy condition 2 or condition 3. For example, the X direction may refer to the length direction when observing the upper surface of the solar cell (100) as in FIGS. 1 to 3. For example, the Y direction may refer to a direction perpendicular to the X direction that is included in the upper surface when observing the upper surface of the solar cell (100) as in FIGS. 1 to 3. For example, the Y direction may refer to the width direction.

[0062] For example, the distance (D) between adjacent holes in the X direction may mean the length of the shortest line formed when a line is extended from each point included in the outline of the hole (H) to any point on the outline of the adjacent hole (H) parallel to the X direction.

[0063] For example, a hole adjacent in the X direction may refer to the hole closest to the selected hole among holes located in the X direction from the selected hole. For example, a hole adjacent in the X direction may also include the hole closest to the selected hole among holes located in the -X direction from the selected hole.

[0064] For example, if there are 2 or more adjacent holes in the X direction, the distance between adjacent holes can be defined for each adjacent hole.

[0065] For example, when referring to FIG. 2, the hole formed at the bottom left of the holes formed in the solar cell (100) is defined as the first hole (H1). The distance (D1) between the first hole and the adjacent hole can be defined as the shortest length (D1) of the lines formed parallel to the X direction from each point included in the outer line of the first hole (H1) to a point included in the outer line of the adjacent hole as shown in FIG. 2.

[0066] According to one embodiment, among the plurality of holes (H), the number of combinations of the first hole (H1) and the second hole (H2) satisfying condition 2 may be 2 or more.

[0067] Referring to FIG. 2, when the bottom left hole is set as the first hole (H1), the distance (D1) to the first hole (H1) and the adjacent hole in the X direction from the first hole (H1) may differ from the distance (D2) to the second hole (H1) and the adjacent hole in the X direction from the second hole (H1) when the top center hole is set as the second hole (H2).

[0068] For example, if the number of combinations of the first hole (H1) and the second hole (H2) satisfying condition 2 among the plurality of holes (H) is 2 or more, with reference to FIG. 2, there may be at least one additional hole combination satisfying condition 2 in addition to the combination of the bottom left hole (H1) and the top middle hole (H2).

[0069] According to one embodiment, the number of combinations of the first hole (H1) and the second hole (H2) satisfying condition 2 among the plurality of holes (H) may be 3 or more, 5 or more, or 10 or more.

[0070] According to one embodiment, any two holes among the plurality of holes (H) can be selected, and condition 2 can be satisfied.

[0071] For example, the distance (D) between adjacent holes in the Y direction may mean the length of the shortest line formed when a line is extended from each point included in the outline of the hole (H) to any point on the outline of the adjacent hole (H) parallel to the Y direction.

[0072] For example, a hole adjacent in the Y direction may refer to the hole located closest to the selected hole among the holes located in the Y direction from the selected hole. For example, a hole adjacent in the Y direction may also include the hole formed closest among the holes located in the -Y direction from the selected hole.

[0073] For example, if there are 2 or more adjacent holes in the Y direction, the distance between adjacent holes can be defined for each adjacent hole.

[0074] For example, when referring to FIG. 3, the hole formed at the bottom left of the holes formed in the solar cell (100) is defined as the third hole (H3). The distance (D3) between the third hole and the adjacent hole can be defined as the shortest length (D3) of the lines formed parallel to the Y direction from each point included in the outer line of the third hole (H1) to a point included in the outer line of the adjacent hole as shown in FIG. 3.

[0075] According to one embodiment, the number of combinations of the third hole (H3) and the fourth hole (H4) satisfying condition 3 among the plurality of holes (H) may be 2 or more.

[0076] Referring to FIG. 3, when the bottom left hole is set as the third hole (H3), the distance (D3) to the third hole (H3) and the adjacent hole in the Y direction from the third hole (H3) may differ from the distance (D4) to the fourth hole (H4) and the adjacent hole in the Y direction from the fourth hole (H4) when the top right hole is set as the fourth hole (H4).

[0077] For example, if the number of combinations of the third hole (H3) and the fourth hole (H4) satisfying condition 3 among the plurality of holes (H) is 2 or more, with reference to FIG. 3, there may be at least one additional hole combination satisfying condition 3 in addition to the combination of the lowest left hole (H3) and the highest middle hole (H4).

[0078] According to one embodiment, the number of combinations of the third hole (H3) and the fourth hole (H4) satisfying condition 3 among the plurality of holes (H) may be 3 or more, 5 or more, or 10 or more.

[0079] According to one embodiment, any two holes among the plurality of holes (H) can be selected, and condition 3 can be satisfied.

[0080] According to one embodiment, the plurality of holes (H) can satisfy condition 2 and condition 3 simultaneously.

[0081] According to one embodiment, the size of each of the plurality of holes (H) may be 1 μm to 5 mm. When the diameter of the holes satisfies the above range, it may be formed to be 1 μm or larger so as to allow all light in the visible light region to pass through and to enable fabrication by a photolithography process. Here, the size of the hole (H) refers to the largest value among the line segments connecting two vertices in the polygon forming the base of the polygonal prism when the hole (H) is a polygonal prism, and refers to the diameter of the circle forming the base of the cylinder when the hole (H) is a cylinder.

[0082] According to one embodiment, the size of each of the plurality of holes (H) may be 1 μm to 5 mm, 100 μm to 1 mm, 150 μm to 1 mm, or 200 μm to 1 mm.

[0083] According to one embodiment, the distance (D) between the holes (H) included in the plurality of holes (H) may be greater than 0㎛ and less than or equal to 5mm, 50㎛ to 1mm, 100㎛ to 1mm, or 150㎛ to 1mm.

[0084] According to one embodiment, the area in which the plurality of holes (H) are formed in the solar cell (100) may be 0 to 90% of the total area of ​​the solar cell. For example, the area in which the plurality of holes (H) are formed may refer to the ratio of the area in which the plurality of holes (H) are formed to the total area of ​​the upper surface of the solar cell. For example, the area in which the plurality of holes (H) are formed in the solar cell (100) may be 10 to 50%, 10 to 40%, 10 to 30%, or 15 to 25% of the total area of ​​the solar cell. For example, the solar cell (100) according to FIGS. 1 to 3 may differ from the solar cell (200) according to FIG. 4, which is a comparative example, in that the area in which the plurality of holes (H) are formed is the same as that of the solar cell (200) according to FIG. 4, which is a comparative example, but the holes (H) may include various shapes or the holes (H) may be irregularly arranged.

[0085] With reference to FIGS. 5 to 7, a solar cell including a plurality of holes according to one embodiment of the present invention will be described in more detail.

[0086] A solar cell (100, 200, 300) according to one embodiment of the present invention may include: a crystalline silicon substrate (110, 210, 310); a first layer (120, 220, 320) located on an upper surface (S1) or a lower surface (S2) of the crystalline silicon substrate and forming a PN junction with the crystalline silicon substrate; a first electrode portion (140, 240, 340) electrically connected to the first layer (120, 220, 320); a second layer (130, 230, 330) located on a lower surface (S2) of the crystalline silicon substrate; and a second electrode portion (150, 250, 350) electrically connected to the second layer (130, 230, 330).

[0087] A plurality of holes (H) penetrating the solar cell (100, 200, 300) can penetrate the components included in the solar cell (100, 200, 300) from the upper surface (S1) to the lower surface (S2) of the crystalline silicon substrate. A plurality of holes (H) penetrating the solar cell (100, 200, 300) can penetrate all the components included in the solar cell (100, 200, 300) from the upper surface (S1) to the lower surface (S2) of the crystalline silicon substrate. For example, the hole (H) may penetrate a crystalline silicon substrate (110, 210, 310) and penetrate a first layer (120, 220, 320) and a first electrode portion (140, 240, 340) and / or a second layer (130, 230, 330) and a second electrode portion (150, 250, 350).

[0088] According to one embodiment, the first layer (120, 220, 320) is disposed on the upper surface (S1) of the crystalline silicon substrate (110, 210, 310), the second layer (130, 230, 330) is disposed on the lower surface (S2) of the crystalline silicon substrate (110, 210, 310), and the plurality of holes (H) can penetrate the first layer (120, 220, 320) and the second layer (130, 230, 330).

[0089] With reference to FIG. 6, a first layer (220) and a first electrode portion (240) are sequentially stacked on an upper surface (S1) of a crystalline silicon substrate (210) such that the first layer (220) is positioned between the upper surface (S1) and the first electrode portion (240), and a second layer (230) and a second electrode portion (250) are sequentially stacked on a lower surface (S2) of a crystalline silicon substrate (210) such that the second layer (230) is positioned between the lower surface (S2) and the second electrode portion (250). In this case, the plurality of holes (H) can penetrate the first layer (220) and the first electrode portion (240), the crystalline silicon substrate (210), and the second layer (230) and the second electrode portion (250).

[0090] According to one embodiment, a first layer (120, 220, 320) and a second layer (130, 230, 330) are alternately arranged on the lower surface (S2) of the crystalline silicon substrate (110, 210, 310), and the plurality of holes (H) can each penetrate the first layer (120, 220, 320) or the second layer (130, 230, 330).

[0091] For example, when the first layer (120, 220, 320) and the second layer (130, 230, 330) are disposed on the lower surface (S2) of the crystalline silicon substrate (110, 210, 310), the lower surface (S2) includes an area where the first layer (120, 220, 320) is disposed and an area where the second layer (130, 230, 330) is disposed, and the area where the first layer (120, 220, 320) is disposed and the area where the second layer (130, 230, 330) is disposed may be disposed alternately. The first layer (120, 220, 320) and the second layer (130, 230, 330) may be disposed spaced apart. As the first layer (120, 220, 320) and the second layer (130, 230, 330) are spaced apart, the recombination of electrons and holes collected from them can be prevented.

[0092] With reference to FIG. 7, a first layer (320) and a first electrode portion (340) are sequentially stacked on a lower surface (S2) of a crystalline silicon substrate (310) such that the first layer (320) is positioned between the lower surface (S2) and the first electrode portion (340), and a second layer (330) and a second electrode portion (350) are sequentially stacked on a lower surface (S2) of a crystalline silicon substrate (310) such that the second layer (330) is positioned between the lower surface (S2) and the second electrode portion (350). In this case, the plurality of holes (H) can penetrate the crystalline silicon substrate (310) and penetrate the first layer (320) and the first electrode portion (340) or the second layer (330) and the second electrode portion (350). For example, among the plurality of holes (H), the first hole (H1) may penetrate the crystalline silicon substrate (310), the first layer (320), and the first electrode portion (340), and the second hole (H2) may penetrate the crystalline silicon substrate (310), the second layer (330), and the second electrode portion (350). The first electrode portion (340) and the second electrode portion (350) may be spaced apart. As the first electrode portion (340) and the second electrode portion (350) are spaced apart, the recombination of electrons and holes collected from them can be prevented.

[0093] The crystalline silicon substrate (110, 210, 310) may be formed of single-crystal or polycrystalline silicon and may have a first conductivity type. The first conductivity type may be an N-type or P-type conductivity type. For example, the crystalline silicon semiconductor substrate (110) may be doped with group 5 elements such as P, As, Sb, etc. as N-type impurities. As another example, the crystalline silicon semiconductor substrate (110, 210, 310) may be implemented as a P-type by doping with group 3 elements such as B, Ga, In, etc. as P-type impurities.

[0094] Additionally, the crystalline silicon semiconductor substrate (110, 210, 310) may include a plurality of holes (H) penetrating the crystalline silicon semiconductor substrate (110, 210, 310) from the upper surface (S1) to the lower surface (S2). The plurality of holes (H) can allow all light in the visible light region to pass through, and accordingly, the solar cell (100, 200, 300) may have a colorless, i.e., transparent property as no specific color is expressed.

[0095] Meanwhile, although not shown in the drawings, the light-receiving surface of the crystalline silicon semiconductor substrate (110, 210, 310) may include various shapes of uneven structures (not shown), such as pyramids, squares, and triangles. The uneven structure (not shown) reduces the reflectance of light incident on the crystalline silicon semiconductor substrate (110, 210, 310), thereby improving the photoelectric conversion efficiency of the solar cell (100, 200, 300).

[0096] The first layer (120) can form a PN junction with a crystalline silicon semiconductor substrate (110, 210, 310). For example, the first layer (120, 220, 320) may be an emitter layer formed by doping with an impurity having a second conductivity type different from the first conductivity type. Accordingly, the upper surface (S1) or lower surface (S2) of the crystalline silicon semiconductor substrate (110) is not a clearly distinct region and can be understood as a region where a PN junction is formed.

[0097] For example, if the crystalline silicon semiconductor substrate (110, 210, 310) has a P-type conductivity type, the first layer (120, 220, 320) may have an N-type conductivity type. If the crystalline silicon semiconductor substrate (110, 210, 310) has an N-type conductivity type, the first layer (120, 220, 320) may have a P-type conductivity type. For example, if the crystalline silicon semiconductor substrate (110, 210, 310) is doped with N-type impurities, the first layer (120, 220, 320) may be doped with P-type impurities, and conversely, if the crystalline silicon semiconductor substrate (110, 210, 310) is doped with P-type impurities, the first layer (120, 220, 320) may be doped with N-type impurities. If the first layer (120, 220, 320), which is an emitter layer, and the crystalline silicon semiconductor substrate (110, 210, 310) have opposite conductivity types, a PN junction is formed at the interface between the crystalline silicon semiconductor substrate (110, 210, 310) and the first layer (120, 220, 320), and when light is irradiated onto the PN junction, a photovoltaic power can be generated by the photoelectric effect.

[0098] The second layer (130, 230, 330) may be a back electric field layer (BSF) doped with impurities having the same first conductivity type as the crystalline silicon semiconductor substrate (110, 210, 310). Accordingly, the lower surface (S2) of the crystalline silicon semiconductor substrate (110, 210, 310) is not a clearly separated region and can be understood as a region that partitions the back electric field layer (BSF) in the crystalline silicon semiconductor substrate (110, 210, 310).

[0099] The second layer (130, 230, 330), which is a back field layer (BSF), can prevent carriers from moving to the back side of the crystalline silicon substrate (110, 210, 310) and recombining, thereby increasing the open-circuit voltage (Voc) of the solar cell (100, 200, 300) and improving the efficiency of the solar cell (100, 200, 300).

[0100] According to one embodiment, either of the first layer (120, 220, 320) and the second layer (130, 230, 330) may be an electron transport layer containing an electron transport material, and the other of the first layer (120, 220, 320) and the second layer (130, 230, 330) may be a hole transport layer containing a hole transport material. For example, when the crystalline silicon semiconductor substrate (110, 210, 310) is an N-type semiconductor substrate, the first layer (120, 220, 320) included in the solar cell (100, 200, 300) may be a hole transport layer, and the second layer (130, 230, 330) may be an electron transport layer. At this time, the first layer (120, 220, 320), which is a hole transport layer, forms a PN junction with a crystalline silicon semiconductor substrate (110, 210, 310), and the second layer (130, 230, 330), which is an electron transport layer, can perform the same role as the back electric field layer.

[0101] The hole transport layer may comprise a transition metal oxide having a high work function. For example, the hole transport layer may be molybdenum oxide (MoO₂). x ), Vanadium oxide (V2O x ), Tungsten oxide (WO x ), Nickel oxide (NiO x It may include ) etc.

[0102] The electron transport layer may include an alkali metal compound having a low work function. For example, the electron transport layer may include lithium fluoride (LiF), cesium fluoride (CsF), cesium oxide (Cs2O), calcium / aluminum (Ca / Al), etc.

[0103] The first electrode part (140, 240, 340) and the second electrode part (150, 250, 350) collect carriers generated by light irradiation and become a path for the carriers to move to an external electronic device electrically connected to the solar cell (100, 200, 300).

[0104] The first electrode portion (140, 240, 340) may be located on the light-receiving surface or the rear surface of the solar cell (100, 200, 300), and the second electrode portion (150, 250, 350) may be located on the rear surface of the solar cell (100, 200, 300). The light-receiving surface of the solar cell (100, 200, 300) corresponds to the upper surface (S1) of the crystalline silicon semi-pore substrate (110, 210, 310), and the rear surface of the solar cell (100, 200, 300) may correspond to the lower surface (S2) of the crystalline silicon semi-pore substrate (110, 210, 310).

[0105] For example, the first electrode portion (140, 240) is disposed on the light-receiving surface of the solar cell (100, 200) and may have a microgrid pattern. The line width of the microgrid pattern may be several μm to 1 mm, and thereby the aperture ratio of the first electrode portion (140, 240) may be 90% or more. Accordingly, the phenomenon of incident light being blocked by the first electrode portion (140, 240) can be minimized.

[0106] When the first electrode portion (140, 240) has the microgrid pattern, the plurality of holes (H) may be arranged in the space between the microgrid patterns. Light incident on the solar cell (100, 200, 300) passes through the plurality of holes (H), and accordingly, the solar cell (100, 200, 300) may be transparent. On the other hand, the second electrode portion (150, 250, 350) may be formed on the rear surface of the solar cell (100, 200, 300).

[0107] The first electrode portion (340) and the second electrode portion (350) may be alternately arranged on the rear surface of the solar cell (300). For example, the first electrode portion (340) and the second electrode (350) may have a linear structure and may be alternately arranged on the rear surface of the solar cell (300) so as not to overlap each other.

[0108] The first electrode portion (140, 240, 340) and the second electrode portion (150, 250, 350) may be transparent electrodes formed by including at least one of ITO, IZO (In-ZnO), GZO (Ga-ZnO), AZO (Al-ZnO), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), IrOx, RuOx, RuOx / ITO, Ni / IrOx / Au, and Ni / IrOx / Au / ITO. When the first electrode portion (140, 240, 340) and the second electrode portion (150, 250, 350) are transparent electrode layers, the plurality of holes (H) may have a shape that penetrates the entire solar cell (100, 200, 300), including the first electrode portion (140, 240, 340).

[0109] The solar cell (100, 200, 300) may further include at least one of a protective film (170, 260, 360), an anti-reflection film (160), an optical film (180, 380), and an anti-adhesion coating layer (not shown) disposed on the upper surface (S1) of the crystalline silicon substrate (110, 210, 310).

[0110] According to one embodiment, the optical film (180, 380) is positioned on the first layer (120, 220, 320) and can cover the first electrode portion (140, 240, 340) and the anti-reflection film (160).

[0111] For example, a protective film (170, 260, 360), an anti-reflection film (160), an optical film (180, 380), and an anti-adhesion coating layer (not shown) may be sequentially laminated on the first layer (120). For example, the plurality of holes (H) may penetrate the anti-reflection film (160), the optical film (180, 380), the protective film (170, 260, 360), and the anti-adhesion coating layer.

[0112] If the solar cell (100, 200, 300) further includes the protective film (170, 260, 360) or the anti-reflection film (160), the protective film (170, 260, 360) or the anti-reflection film (160) may cover at least a portion of the inner surface of the plurality of holes (H). The protective film or the anti-reflection film may completely cover the inner surface of the plurality of holes.

[0113] Referring again to FIG. 5, the solar cell (100) may include an anti-reflection film (160) located on a first layer (120). Additionally, the solar cell (100) may further include a protective film (170) located between the anti-reflection film (160) and the first layer (120). In this case, the first electrode portion (140) may be electrically connected to the first layer (120) by penetrating the anti-reflection film (160) and the protective film (170).

[0114] The anti-reflection film (160) can passivate defects present on the surface or in the bulk of the first layer (120), i.e., the emitter layer, and reduce the reflectivity of incident sunlight. When defects present in the emitter layer are passivated, minority carrier recombination sites are removed, and the open-circuit voltage (Voc) of the solar cell (100) increases. In addition, when the reflectivity of sunlight is reduced, the amount of light reaching the PN junction increases, and the short-circuit current (Isc) of the solar cell (100) increases. Therefore, the photoelectric conversion efficiency of the solar cell (100) can be improved.

[0115] The anti-reflection film (160) may have a single film selected from the group consisting of, for example, silicon nitride film, silicon nitride film containing hydrogen, silicon oxide film, silicon oxide nitride film, MgF2, ZnS, TiO2, and CeO2, or a multilayer film structure in which two or more films are combined. The anti-reflection film (160) is formed to cover not only the upper surface of the first layer (120) but also the inner surfaces of a plurality of holes (H), thereby reducing the reflection of light passing through the holes (H) and inducing absorption into the solar cell (100).

[0116] The anti-reflection film (160) may include surface structures of various irregular shapes, such as pyramids, squares, and triangles, on its surface. The surface structures can be formed by various methods, such as dry etching, or by increasing the surface roughness of the anti-reflection film (160). The surface structures of the anti-reflection film (160) can reduce the reflection of incident light, thereby improving the photoelectric conversion efficiency of the solar cell (100).

[0117] A protective film (170) is formed on the upper surface of a crystalline silicon semiconductor substrate (110) to prevent the recombination of photocharges generated by the incidence of sunlight and to reduce defects caused by lattice mismatch resulting from the anti-reflection film (160) being formed directly on the crystalline silicon semiconductor substrate (110). This protective film (170) may be formed by including a-Si, a-SiOx, or a-SiC. In particular, since a-SiOx and a-SiC have a bandgap energy of 1.8 eV or more, the light absorption coefficient is small, so it can prevent a decrease in the amount of light incident on the crystalline silicon semiconductor substrate (110). However, it is not limited thereto, and the protective film (170) may be formed from an inorganic film such as Al2O3. The protective film (170) may be formed to cover the sides of a plurality of holes (H), similar to the anti-reflection film (160).

[0118] An optical film (180) may be disposed on an anti-reflection film (160). According to one embodiment, the structure has a plurality of holes (H) that simultaneously penetrate the solar cell (10) and the optical film (18), thereby preventing refraction or scattering of incident light entering through the plurality of holes (H). Therefore, an object located on the back of the solar cell can be clearly recognized. In addition, the optical film (180) can compensate for the resulting decrease in efficiency even if the area of ​​the crystalline silicon substrate (110) is reduced due to the formation of holes within the solar cell (100), thereby improving the light transmittance and photoelectric conversion efficiency of the solar cell (100).

[0119] The optical film (180) may include polygonal structures on its surface. For example, the polygonal structures may include cylindrical, pyramidal, rectangular prismal, or a combination thereof. By including the polygonal structures on the surface, the reflectance of incident light incident on a solar cell (100), for example, a solar cell, is reduced, and the absorption of incident light incident at various angles is facilitated, thereby increasing the light absorption rate and improving the photoelectric conversion efficiency.

[0120] The optical film (180) can absorb light in a wavelength band of 700 nm or more, for example, infrared light. By doing so, the light absorption rate reduced by a plurality of holes is compensated, thereby allowing light transparency while maintaining the photoelectric conversion efficiency of a conventional crystalline silicon-based solar cell.

[0121] The optical film (180) may include a thermosetting resin or a UV-curing resin. For example, the optical film may include polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), ethylene vinyl acetate (EVA), polyimide (PI), or a combination thereof.

[0122] The optical film (180) may further include an anti-adhesion coating layer (not disclosed) on its surface. The anti-adhesion coating layer (not disclosed) prevents external substances from adhering to the optical film (180). If external substances, such as dust, adhere to the optical film, the light absorption capacity may be impaired.

[0123] The above anti-adhesion coating layer (not disclosed) may include a self-assembling monolayer coating layer. The self-assembling monolayer coating layer refers to a monomolecular film that is spontaneously formed on the surface. The self-assembling monolayer coating layer may have a thickness of several nanometers to tens of nanometers. Due to this thin coating layer, the light absorption rate is not reduced even when the self-assembling monolayer coating layer is added, and a decrease in light absorption rate caused by the anti-adhesion coating layer can be prevented.

[0124] Generally, molecules forming a self-assembling monolayer coating layer consist of a reactive group that bonds to the substrate surface, an alkane chain that enables the formation of the monolayer, and a functional group that determines the physical properties of the coating layer. Such a self-assembling monolayer coating layer forms a very robust coating layer by forming a direct chemical bond with the substrate surface through the reactive group. Here, the reactive group may form ionic bonds, charge-transfer complexes, or covalent bonds depending on its interaction with the substrate. Self-assembling molecules that form ionic bonds may include, for example, alkanes. Self-assembling molecules that form charge-transfer complexes may include, for example, organic sulfur. Self-assembling molecules that form covalent bonds may include, for example, organosilicon.

[0125] The self-assembling monolayer coating layer may include organosilicon molecules. For example, the organosilicon self-assembling molecule may include fluoro-octyl-trichloro-silane.

[0126] The self-assembling single-layer coating layer may be hydrophobic. Accordingly, it has excellent self-cleaning capabilities against contaminants. Hydrophobicity was determined by measuring the water droplet contact angle of a solar cell including a self-assembling single-layer coating layer according to one embodiment of the present invention and a solar cell not including a self-assembling single-layer coating layer. It was found that the self-assembling single-layer coating layer has a water droplet contact angle of 110°, indicating high hydrophobicity. Therefore, the self-assembling single-layer coating layer not only prevents contaminants from adhering to the surface of an optical film but also has excellent self-cleaning capabilities due to its hydrophobicity.

[0127] Although the above description refers to the embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

[0128] [Explanation of the symbol]

[0129] 100, 200, 300: Solar cells

[0130] 110, 210, 310: Crystalline silicon semiconductor substrates

[0131] 120, 220, 320: 1st floor

[0132] 130, 230, 330: 2nd floor

[0133] 140, 240, 340: First electrode part

[0134] 150, 250, 350: Second electrode part

[0135] 160: Anti-reflective coating

[0136] 170, 260, 360: Shield

[0137] 180, 380: Optical film

Claims

1. A solar cell comprising a plurality of holes penetrating the solar cell, The above plurality of holes is a solar cell satisfying at least one of the following conditions 1 to 3: <Condition 1> The above plurality of holes includes two or more types. <Condition 2> The distance (D1) between a first hole, which is any one of the plurality of holes, and a hole adjacent to the first hole in the X direction, and the distance (D2) between a second hole, which is any one of the plurality of holes, and a hole adjacent to the second hole in the X direction are different from each other. <Condition 3> The distance (D3) between the third hole, which is one of the plurality of holes, and the hole adjacent to the third hole in the Y direction, and the distance (D4) between the fourth hole, which is one of the plurality of holes, and the hole adjacent to the fourth hole in the Y direction are different from each other.

2. In Paragraph 1, The above plurality of holes are a solar cell satisfying the above condition 1.

3. In Paragraph 1, A solar cell in which the shape of the hole is at least one of an elliptical shape, a cross shape, an X shape, a polygonal shape, or a star shape.

4. In Paragraph 1, The above plurality of holes is a solar cell satisfying at least one of the above condition 2 and the above condition 3.

5. In Paragraph 4, A solar cell in which the number of combinations of the first hole and the second hole satisfying condition 2 among the plurality of holes is 2 or more.

6. In Paragraph 4, A solar cell in which the number of combinations of the third hole and the fourth hole satisfying condition 3 among the plurality of holes is 2 or more.

7. In Paragraph 1, A solar cell in which the size of each of the plurality of holes is 1 μm to 5 mm.

8. In Paragraph 1, A solar cell in which the area in which the plurality of holes are formed is greater than 0% and less than or equal to 90% of the total area of ​​the solar cell.

9. In Paragraph 1, The above solar cell Crystalline silicon substrate; A first layer disposed on the upper or lower surface of the crystalline silicon substrate and forming a PN junction with the crystalline silicon substrate; A first electrode portion electrically connected to the first layer above; A second layer located on the lower surface of the crystalline silicon substrate; and A solar cell comprising a second electrode portion electrically connected to the second layer.

10. In Paragraph 9, A solar cell comprising at least one of a protective film, an anti-reflective film, an optical film, and an anti-adhesion coating layer disposed on the upper surface of the crystalline silicon substrate.

11. In Paragraph 10, In the case of including the above protective film or the above anti-reflective film, A solar cell, wherein the protective film or the anti-reflective film covers at least a portion of the inner surface of the plurality of holes.

12. In Paragraph 9, The above crystalline silicon substrate has a first conductivity type, The first layer is an emitter layer doped with impurities having a second conductivity type opposite to the first conductivity type, and A solar cell in which the second layer is a back electric field layer doped with impurities having the first conductivity type.

13. In Paragraph 9, A solar cell, wherein either of the first layer and the second layer is an electron transport layer comprising an electron transport material, and the other of the first layer and the second layer is a hole transport layer comprising a hole transport material.

14. In Paragraph 9, The first layer and the second layer are alternately arranged on the lower surface of the crystalline silicon substrate, and The above plurality of holes each penetrate the first layer or the second layer, forming a solar cell.

15. In Paragraph 9, The first layer is disposed on the upper surface of the crystalline silicon substrate, and The above second layer is disposed on the lower surface of the crystalline silicon substrate, and The above plurality of holes penetrate the first layer and the second layer, forming a solar cell.

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